Diffusion transfer process



United Patent 01 3,433,634 DIFFUSION TRANSFER PROCESS Louis Maria DeHaes, Edegem, Belgium, assignor to Gevaert Photo-Producten N.V.Mortsel-Antwerp, Belgium, a Belgian company No Drawing. Filed Feb. 5,1964, Ser. No. 342,778

U.S. Cl. 96-29 Claims Int. Cl. G03c 5/54 The present invention relatesto an improved silver halide diffusion transfer process. Photographicmaterials and treating compositions which enable the said improvedprocess will be described more in detail further in the description.

It is an object of the present invention to obtain dilfusion transferprints in an accelerated Way.

It is another object of the present invention to reduce the treatingliquid to a composition which is substantially free of developingagents.

It is a further object of the present invention to provide a methodwhich enables obtaining several diffusion transfer prints from a sameimage-wise exposed lightsensitive silver halide material.

It is a still further object of the present invention to producediffusion transfer prints which are practically immediately dry afterthey have been obtained.

It is another object to reduce the quantity of silver halide in thelight-sensitive material.

It is still another object to smiplify the composition of the support ofthe light-sensitive and/or the image-receiving material to a commonpaper support not specially intended for photographic purposes.

These and still other objects as well as advantages of this inventionwill appear hereinafter.

According to the present invention a diffusion transfer image isobtained by image-Wise exposing a light-sensitive material (a)comprising a support, a light-sensitive silver halide emulsion layer anda layer of a swellable colloid on top of said light-sensitive layer, and(b) containing hydroquinone and a B-pyrazolidone developing compound,

contacting said light-sensitive material, in the presence of an alkalinetreating liquid which is substantially free of developing agents, withan image-receiving material containing development nuclei and/orsubstances capable of forming such nuclei in situ and separating thecontacted materials from each other.

The support of the light-sensitive material is mostly a paper supportsuch as of common paper.

The composition of the silver halide emulsion layer may be as usual inthe art of diffusion transfer. The emulsion composition is not criticalprovided its silver salt(s) is (are) capable of development anddiffusion in the exposed and non-exposed areas respectively with therapidity required in diffusion transfer processes. Gelatin silverchloride emulsions, which may contain silver bromide or silver iodide,and to which other ingredients have been added so as to impart thedesired emulsion characteristics, are preferably used. Thelight-sensitive silver halide emulsion layer has to be hardened in ausual way by a suitable hardening agent such as formaldehyde. Preferablythe silver halide emulsion layer contains per sq. m. of light-sensitivematerial an amount of silver halide equivalent to from 0.2 to 2 g. ofsilver nitrate. In the known diffusion transfer processes the optimumresults are mostly obtained with a quantity of silver halide equivalentto about 1.5 g. of silver nitrate per sq. m. of lightsensitive material.According to the present invention, however, these optimum results mayalready be obtained with quantities of silver halide equivalent to about0.5 g. of silver nitrate per sq. m. of light-sensitive material.

This effect is probably due to the presence of the greater or all partof the developing agents in the light-sensitive material. The thicknessof the light-sensitive layer is not very critical.

Suitable swellable colloids for the layer coated on top of thelight-sensitive layer are ac. the following waterpermeable colloids:methylcellulose, hydroxyethylcellulose, hydroxyethyl-starch,hydroxypropyl-starch, sodium alginate, propylene glycol ester of alginicacid, gum trag-acanth, starch, poly(vinylalcohol), poly( acrylic acid),poly(acryl amide), poly(vinyl pyrrolidone), poly(oxyethylene),copoly(methyl vinyl ether/maleic acid), etc. The thickness of this toplayer varies among others according to the nature of the colloid chosenand the viscosity of the used colloid solution, but mostly the top layeris only a thin layer. Preferably it is not hardened. During separatingthe light-sensitive material and the image-receiving material from eachother probably a thin stratum of said top layer is transferred to theimage-receiving material.

The light-sensitive material comprises hydroquinone and a 3-pyrazolidonedeveloping compound. Each of these compounds is preferably present in atleast one waterpermeable layer of the light-sensitive material such asthe silver halide emulsion layer and the top layer on the silver halideemulsion layer. Hydroquinone as well as the 3-pyrazolidone developingcompound preferably are present in an amount of from 0.1 to 5 g. per sq.m. of lightsensitive material. Specially suited 3-pyrazolidonedeveloping compounds correspond to the following general formula:

wherein:

R represents an aryl radical or a substituted aryl radical,

R represents a hydrogen atom or an acyl radical such as an acetylradical, and

each of R R R and R (the same or different) represents a hydrogen atom,an alkyl radical, a substituted alkyl radical, an aryl radical or asubstituted aryl radical.

Good results can be obtained with the following compounds correspondingto the above formula:

1-phenyl-3-pyrazolidone 1-(-m-tolyl)-3-pyrazolidone 1-phenyl-2-acetyl-3-pyrazo1idone 1-phenyl-4-methyl-3-pyrazolidone1-phenyl-5-methyl-3-pyrazolidone 1-phenyl-4,4-dimethyl-3-pyrazolidonel-phenyl-S ,5 -dimethyl-3-pyrazolidone 1,5 -diphenyl-3-pyrazolidone1-(m-tolyl)-5-phenyl-3-pyrazolidone l-(p-tolyl)-5-phenyl-3-pyrazolidoneInto the light-sensitive emulsion layer and/or into a water-permeablelayer situated at the same side of the support as the light-sensitiveemulsion layer usual substances beneficial or essential to the processmay be incorporated, for instance softening agents, stabilizing agents,black-toning agents and the like.

The image-receiving material for being used in the present process maycomprise a support of for instance paper, film, textile, ceramic metaletc. Mostly a paper support is used. The image-receiving materialcomprises development nuclei and/or substances capable of forming suchnuclei in situ. These nuclei and/or substances capable of forming suchnuclei in situ may be incorporated in the support itself, e.g. in thesizing layer of a paper sheet, or in a separate layer applied to thesupport, such as a baryta layer coated on a paper support or anotherlayer e.g. of gelatin applied to a support, such as a paper supportwhich my be baryta-coated. In case the imagereceiving material is notentirely soaked in the treating liquid, but is only moistened by thewetted light-sensitive material at the nuclei side, it is oftenadvantageous to have the rear side of the image-receiving materialprovided too with one or more layers preventing curling of theimage-receiving material in this way. One of these layers may be anuclei-containing layer too, so that a material may be obtained suitedfor producing a diffusion transfer image on each side.

Development nuclei for silver halide complexes suitable for promotingthe formation of the silver containing diffusion transfer image are thesulphides of heavy metals e.g. of antimony, bismuth, cadmium, cobalt,lead, nickel, silver and zinc. Selenides, polysulphides, polyselenides,mercaptanes, stannous halides, heavy metals or their salts and foggedsilver halides are also suitable for this purpose. The complex salts oflead sulphide and zinc sulphide are effective either in themselves ormixed with thioacetamide, dithiobiuret and dithiooxamide. Among theheavy metals, silver, gold, platinum, palladium and mercury, preferablyin their colloidal form, are to be mentioned. The noble metals amongthem are the most active. The substances capable of forming developmentnuclei in situ do so by reacting with a compound or compounds present inthe light-sensitive or image-receiving material, e.g., by reacting withdiffusing complexed silver halide.

The image-receiving material may also comprise in at least one of itslayers usual ingredients for the diffusion transfer process such assodium sulphite, a complexing agent for silver halide such as sodiumthiosulphate and black-toning agents. It is specially interesting tohave present in the image-receiving material, e.g. in thenucleicontaining layer, .a quantity of hydroquinone and occasionally atleast one compound selected from the group consisting of alkalimetabisulphites such as potassium metabisulphite, water-solubleinorganic bisulphites and water-soluble aldehyde bisulphites as .apreservative for hydroquinone and in order to obtain diffusion transfercopies keeping a white background in aging. Such an image-receivingmaterial containing hydroquinone and the said bisulphites is describedin the German patent specification 1,129,052. The hydroquinone is mostlypresent in an amount of from 0.1 to 5 g. per sq. m. and the watersolublebisulphite in an amount of from 0.2 to 2 g. per

sq. m.

The treating liquid for carrying out the process of the presentinvention is an alkaline, preferably aqueous, liquid whcih issubstantially free of developing agents. For alkalizing the treatingliquid basic compounds are added such as sodium hydroxide, potassiumhydroxide, lithium hydroxide, ammonium hydroxide, sodium carbonate,sodium phosphate, etc. For a compound which is weak in this respect,e.g. sodium phosphate, it is ap propriate to use an amount of theanhydrous salt of from 50 to 200 g. per liter. In the case of a compoundwhich imparts a high degree of alkalinity, e.g. sodium hydroxide, anamount of from 5 to 20 g. will sufiice.

The treating liquid may further contain other usual ingredients such assodium sulphite, e.g. in the amount of from to 40 g. per liter, sodiumbromide, a complexing agent for silver halide, a calcium sequesteringcompound and a black-toning agent e.g. 1-phenyl-S-mercapto-tetrazole orsimilar products such as those described in the British patentspecification 561,875 and the Belgian patent specification 502,525.

Since the treating liquid is substantially free of developing substancesit cannot be exhausted by aerial oxidation and consequently may be usedfor fairly a long time before being replaced. This is one of the greatadvantages of the present process.

According to, the present invention, both the light-sensitive and theimage-receiving material may be moistened with treating liquid,whereupon they are brought in contact with each other. It is, however, apreferred embodiment of the present invention to moisten only one of thematerials used, preferably the light-sensitive material, and to bringthis moistened material in contact with the other dry one. Themoistening of at least one of the materials used may occur by means ofwetted rollers e.g. as fully described in the Dutch patent application288,817 (filed Feb. 11, 1963). In this way only one side e.g. theemulsion side of the light-sensitive material may be wetted. In thispatent application also an interesting method is described of separatingthe light-sensitive and the imagereceiving material from each other. Thegreat advantage of wetting the sole light-sensitive material, preferablyby means of wetted rollers, is that the obtained diffusion transfer copyis practically immediately dry and keeps its white background duringstorage, for only a very little quantity of the treating liquid has beenabsorbed.

Another advantage of the present diffusion transfer process is therapidity at which the prints may be obtained. Indeed, a moistening timeof the light-sensitive material with treating liquid of about 3 secondsand a contact time between the light-sensitive and the imagereceivingmaterial of about 5 to 15 seconds mostly may suflice to obtain adiffusion transfer print of good quality.

In order to facilitate the separation of the light-sensitive from theimage-receiving material and to obtain a completely dry diffusiontransfer print, the pressed sandwich of light-sensitive andimage-receiving materials may be subjected to heat.

Finally, according to the invention, it is also possible to obtainseveral diffusion transfer prints from a same imagewise exposedlight-sensitive material by bringing it, in the presence of the treatingliquid, successively in contact with a second, a third, etc.image-receiving material.

The following examples illustrate the present invention.

Example 1 Water cm. 800 Hydroxyethyl starch having a substitution degreeof 0.27 hydroxyethyl groups 40 Ethanol cm. 200 1-phenyl-3-pyrazolidone g5 Hydroquinone g 10 Aqueous formaldehyde, 20% cm. 10

This light-sensitive material is image-wise exposed and then moistenedwith the following treating liquid:

Water cm. 1000 Sodium phosphate g Anhydrous sodium sulfite g 40Anhydrous sodium thiosulfate g 10 This light-sensitive material is thenbrought in contact with a dry image-receiving material consisting of apaper support of g./sq. m. to which a layer from the followingcomposition has been applied at 45 C. in a proportion of 1 liter per 40sq. m.:

The dispersion of cobalt (II) sulfide is prepared at 45 C. from:

Water cm. 78 Gelatin g 2 Aqueous sodium sulfide, 10% cm. 12 Aqueouscobalt (II) nitrate, 10% cm. 11

After a contact time of about 10 seconds the lightsensitive and theimage-receiving material are separated from each other. A practicallycompletely dry diffusion transfer print of excellent quality isobtained.

Example 2 A light-sensitive material as described in Example 1 isprepared with the dilference, however, that the silver halide emulsionlayer is applied in such a way that an amount of silver chlorideequivalent to 0.6 g. of silver nitrate is present per sq. m.

This light-sensitive material is image-wise exposed and then moistened,at the emulsion side only, with a treating liquid as described inExample 1. After 3 to 5 seconds the light-sensitive material is broughtin contact with an image-receiving material for about 8 seconds. Thismaterial may be prepared by coating a paper support of 90 g. per sq. m.in a proportion of 1 liter per 25 sq. rn. with the followingcomposition:

Water cm. 812.5 Gelatin g- 3 0 Dispersion of cobalt (II) sulfide nucleias described in Example 1 cm. 7.5 l-phenyl-5-mercapto-tetrazole inethanol, 1% solution cm. 15 Hydroq'uinone g 37.5 Anhydrous potassiummetabisulfite g 37.5 Aqueous formaldehyde cm. 60

After separating the light-sensitive and image-receiving materialfromleach other, an excellent, dry positive print of the original isobtained.

Example 3 A light-sensitive material is prepared as described in Example2, with the difference, however, that the hydroquinone and the1-phenyl-3-pyrazolidone, instead of being incorporated in the layer ontop of the silver halide emulsion layer, are incorporated in the silverhalide emulsion layer itself in a concentration of 1 g. and 0.5 g.respectively per sq. m. of light-sensitive material.

This light-sensitive material is image-wise exposed and, together withan image-receiving material as described in Example 2, moistened withthe treating liquid of Example l. The light-sensitive and theimage-receiving material are pressed against each other, subjected to aheat treatment and separated from each other. A dry positive print ofgood quality is obtained.

'1 claim:

1. A process for obtaining photographic images according to the silverhalide diffusion transfer process, which comprises:

prising a support, a light-sensitive silver halide emulsion layer and alayer of a swellable colloid on top of said light-sensitive layer, and(b) containing hydroquinone and a 3-pyrazolidone developing compound,

contacting said light-sensitive material, in the presence of an alkalinetreating liquid which is substantially free of developing agents, withan image-receiving material containing hydroquinone and a memberselected from the group consisting of development nuclei and substancescapable of forming such nuclei in situ, and

separating the contacted materials from each other.

2. The process of claim 1, .wherein the light-sensitive silver halideemulsion layer contains per per sq. m. an amount of silver halide whichis equivalent with from 0.2 to 2 g. of silver nitrate.

3. The process of claim 1, wherein the image-receiving material containsfrom 0.1 to 5 g. per sq. m. of hydroquinone and said light-sensitivematerial contains from 0.1 to 5 g. per sq. m. of hydroquinone and said3-pyrazolidone developing compound.

4. The process of claim 1 wherein said light-sensitive material iswetted with said alkaline treating liquid and is thereafter contacted[while wet with dry image-receiving material.

5. The process of claim 4, wherein the sole emulsion side of thelight-sensitive material is wetted with the alkaline treating liquid.

6. A process for obtaining photographic images according to the silverhalide diffusion transfer process, which comprises:

image-wise exposing a light-sensitive material (a) comprising a support,a light-sensitive silver halide emulsion layer and a layer of aswellable colloid on top of said light-sensitive layer, and (b)containing hydroquinone and a 3-pyrazolidone developing compound,

contacting said light-sensitive material in the presence of an alkalinetreating liquid which is substantially free of developing agents, withan image-receiving material containing hydroquinone, at least onecompound selected from the group consisting of alkali metabisulphites,water-soluble inorganic b-isulphites and water-soluble aldehydebisulphites, and a member selected from the group consisting ofdevelopment nuclei and substances capable of forming such nuclei insitu, and

separating the contacted materials from each other.

7. The process of claim 6, wherein the said at least one compound ispresent in the image-receiving material in an amount of from 0.2 to 2.g. per sq. m.

References Cited UNITED STATES PATENTS 2,834,676 5/1958 Stanley et al.96-29 3,261,685 7/1966 De Haes et al. 96-95 FOREIGN PATENTS 767,9782/1-9 57 Great Britain.

J. TRAVIS BROWN, Primary Examiner.

J. P. BRAMMER, Assistant Examiner.

U.S. Cl. X.R.

image-wise exposing a light-sensitive material, (a) com- 9676

1. A PROCESS FOR OBTAINING PHOTOGRAPHIC IMAGES ACCORDING TO THE SILVERHALIDE DIFFUSION TRANSFER PROCESS, WHICH COMPRISES: IMAGE-WISE EXPOSINGA LIGHT SENSITIVE MATERIAL, (A) COMPRISING A SUPPORT, A LIGHT-SENSITIVESILVER HALIDE EMULSION LAYER AND A LAYER OF A SWELLABLE COLLOID ON TOPOF SAID LIGHT-SENSITIVE LAYER, AND (B) CONTAINING HYDROQUINONE AND A3-PYRAZOLIDONE DEVELOPING COMPOUND, CONTACTING SAID LIGHT-SENSITIVEMATERIAL, IN THE PRESENCE OF AN ALKALINE TREATING LIQUID WHICH ISSUBSTANTIALLY FREE OF DEVELOPING AGENTS, WITH AN IMAGE-RECEIVINGMATERIAL CONTAINING HYDROQUINONE AND A MEMBER SELECTED FROM THE GROUPCONSISTING OF DEVELOPMENT NUCLEI AND SUBSTANCES CAPABLE OF FORMING SUCHNUCLEI IN SITU, AND SEPARATING THE CONTACTED MATERIALS FROM EACH OTHER.